git: cfeedadfbde0 - main - reboot: Add sanity checking of write to nextboot.conf

The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=cfeedadfbde084e25ace99a370f3f417b78f5df7

commit cfeedadfbde084e25ace99a370f3f417b78f5df7
Author:     Warner Losh <imp@FreeBSD.org>
AuthorDate: 2024-02-12 18:45:20 +0000
Commit:     Warner Losh <imp@FreeBSD.org>
CommitDate: 2024-02-12 18:45:20 +0000

    reboot: Add sanity checking of write to nextboot.conf
    
    Add sanity checking to the write to nextboot. Move to separate function
    and allow force to override all errors. If we can't write nextboot.conf,
    don't silently fail anymore.
    
    Sponsored by:           Netflix
    Reviewed by:            kevans, kib, markj, jhb
    Differential Revision:  https://reviews.freebsd.org/D43803
---
 sbin/reboot/reboot.c | 47 +++++++++++++++++++++++++++++++++++++----------
 1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/sbin/reboot/reboot.c b/sbin/reboot/reboot.c
index 4eb5e8590589..74f8cf01b3b7 100644
--- a/sbin/reboot/reboot.c
+++ b/sbin/reboot/reboot.c
@@ -49,17 +49,52 @@
 #include <unistd.h>
 #include <utmpx.h>
 
+#define PATH_NEXTBOOT "/boot/nextboot.conf"
+
 static void usage(void) __dead2;
 static uint64_t get_pageins(void);
 
 static bool dohalt;
 
+static void
+write_nextboot(const char *fn, const char *kernel, bool force)
+{
+	FILE *fp;
+
+#define E(...) do {				\
+		if (force) {			\
+			warn( __VA_ARGS__ );	\
+			return;			\
+		}				\
+		err(1, __VA_ARGS__);		\
+	} while (0)				\
+
+	fp = fopen(fn, "w");
+	if (fp == NULL)
+		E("Can't create %s to boot %s", fn, kernel);
+
+	if (fprintf(fp,
+	    "nextboot_enable=\"YES\"\n"
+	    "kernel=\"%s\"\n", kernel) < 0) {
+		int e;
+
+		e = errno;
+		fclose(fp);
+		if (unlink(fn))
+			warn("unlink %s", fn);
+		errno = e;
+		E("Can't write %s", fn);
+	}
+	fclose(fp);
+#undef E
+}
+
 int
 main(int argc, char *argv[])
 {
 	struct utmpx utx;
 	const struct passwd *pw;
-	int ch, howto, i, fd, sverrno;
+	int ch, howto, i, sverrno;
 	bool fflag, lflag, nflag, qflag, Nflag;
 	uint64_t pageins;
 	const char *user, *kernel = NULL;
@@ -147,15 +182,7 @@ main(int argc, char *argv[])
 				errx(1, "%s is not a file", k);
 			free(k);
 		}
-		fd = open("/boot/nextboot.conf", O_WRONLY | O_CREAT | O_TRUNC,
-		    0444);
-		if (fd > -1) {
-			(void)write(fd, "nextboot_enable=\"YES\"\n", 22);
-			(void)write(fd, "kernel=\"", 8L);
-			(void)write(fd, kernel, strlen(kernel));
-			(void)write(fd, "\"\n", 2);
-			close(fd);
-		}
+		write_nextboot(PATH_NEXTBOOT, kernel, fflag);
 	}
 
 	/* Log the reboot. */